A French government spokesman said Wednesday the man who attacked Paris police officers with a hammer at the Notre Dame Cathedral was a student working on his doctoral thesis and had not been suspected of radicalization.

Christopher Castaner said in an interview with RTL radio that police classified the attack as a terrorist act because of what the man said.

French Interior Minister Gerard Collomb said after the attack Tuesday that the man shouted, "It's for Syria."Collomb also told reporters an identification card found on the attacker indicated he was an Algerian student.

A police search of his apartment subsequently found a video in which the man declared allegiance with Islamic State.

The attacker walked up behind three police officers on patrol in the late afternoon, as the square in front of the cathedral was crowded with tourists.

The French prosecutor's office said its counterterrorism unit has launched an investigation into the attack, which occurred as officers patrolled the esplanade in front of the cathedral.

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As the attack unfolded, tourists waiting to enter the cathedral were hurried inside by security personnel. The doors to the cathedral were locked while police reinforcements cleared the square, checking for any accomplices or explosive devices.

The Paris police department said an officer shot and injured the man after he attacked one of the officers with a hammer. Collomb said the policeman is in stable condition. He said both the policeman and his assailant were taken to the hospital.

Collomb said the assailant also possessed kitchen knives, an indication of a trend from "very sophisticated" acts of terrorism to "whatever tools or instruments they can find."

Collomb said the attacker acted on his own. "He was not working in conjunction with any body," he said.

Collomb said he and other European interior ministers will meet soon to better learn how to coordinate the sharing of intelligence in the fight against terrorism.

Paris remains under high security after several terrorist attacks in recent years, including on law enforcement and security personnel.

In April, an attacker shot at a police van on Paris' Champs Elysees. One officer was killed and two others were injured. The attacker was fatally shot by police.

On Saturday, a terror attack on London Bridge and a nearby restaurant killed seven people. The three attackers were shot dead by police.